Water treatment polymers and methods of use thereof

ABSTRACT

New composition of polymers and methods of use are disclosed. The polymers are water soluble and are composed of repeat units formed from an α, β ethylenically unsaturated compound, and repeat units formed from allyl alkylene phosphonates.

CROSS REFERENCE RELATED APPLICATIONS

This is a continuation-in-part of U.S. application Ser. No. 037,484filed April 13, 1987, now U.S. Pat. No. 4,759,851, which is acontinuation of Ser. No. 864,049 filed May 16, 1986, now U.S. Patent4,659,481, which in turn is a continuation of Ser. No. 545,563, filedOct. 26, 1983, now abandoned.

FIELD OF THE INVENTION

The present invention pertains to a composition and method of utilizingsame to control the formation and deposition of scale impartingcompounds in water systems such as cooling, boiler and gas scrubbingsystems.

BACKGROUND OF THE INVENTION

The problem of scale formation and attendant effects have troubled watersystems for years. For instance, scale tends to accumulate on internalwalls of various water systems, such as boiler and cooling systems, andthereby materially lessens the operational efficiency of the system.

Deposits in lines, heat exchange equipment, etc., may originate fromseveral causes. For example, precipitation of calcium carbonate, calciumsulfate and calcium phosphate in the water system leads to anaccumulation of these scale imparting compounds along or around themetal surfaces which contact the flowing water circulating through thesystem. In this manner, heat transfer functions of the particular systemare severely impeded.

Typically, in cooling water systems, the formation of calcium sulfate,calcium phosphate and calcium carbonate, among others, has provendeleterious to the overall efficiency of the cooling water system.Recently, due to the popularity of cooling treatments using high levelsof orthophosphate to promote passivation of the metal surfaces incontact with the system water, it has become critically important tocontrol calcium phosphate crystallization so that relatively high levelsof orthophosphate may be maintained in the system to achieve the desiredpassivation without resulting in fouling or impeded heat transferfunctions which would normally be caused by calcium phosphatedeposition.

Although steam generating systems are somewhat different from coolingwater systems, they share a common problem in regard to depositformation.

As detailed in the Betz Handbook of Industrial Water Conditioning, 8thEdition, 1980, Betz Laboratories, Inc., Trevose, Pa., pages 85-96, theformation of scale and sludge deposits on boiler heating surfaces is aserious problem encountered in steam generation. Although currentindustrial steam producing systems make use of sophisticated externaltreatments of the boiler feedwater, e.g., coagulation, filtration,softening of water prior to its feed into the boiler system, theseoperations are only moderately effective. In all cases, externaltreatment does not in itself provide adequate treatment since muds,sludge, silts and hardness-imparting ions escape the treatment, andeventually are introduced into the steam generating system.

In addition to the problems caused by mud, sludge or silts, the industryhas also had to contend with boiler scale. Although external treatmentis utilized specifically in an attempt to remove calcium and magnesiumfrom the feedwater, scale formation due to residual hardness, i.e.,calcium and magnesium salts, is always experienced. Accordingly,internal treatment, i.e., treatment of the water fed to the system, isnecessary to prevent, reduce and/or retard formation of the scaleimparting compounds and their resultant deposition. The carbonates ofmagnesium and calcium are not the only problem compounds as regardsscale, but also waters having high contents of phosphate, sulfate andsilicate ions either occurring naturally or added for other purposescause problems since calcium and magnesium, and any iron or copperpresent, react with each and deposit as boiler scale. As is obvious,deposition on the structural parts of a steam generating system causespoorer circulation and lower heat transfer capacity, resulting in anoverall loss in efficiency.

SUMMARY OF THE INVENTION

The present invention is directed to new water soluble allyl alkylenephosphonate copolymers and terpolymers for water treatment.Specifically, the novel copolymers of the invention comprise repeatunits having the structure: ##STR1## wherein E in the above formula isthe repeat unit after polymerization of an α, βethylenically unsaturatedcompound, preferably carboxylic acid, amide form thereof, or lower alkyl(C₁ -C₆) ester or hydroxylated lower alkyl (C₁ -C₆) ester of suchcarboxylic acid. Compounds encompassed by E include the repeat unitafter polymerization of acrylic acid, methacrylic acid, acrylamide,maleic acid or anhydride, styrene, styrene sulfonic acid and itaconicacid; and the like. Water soluble salt forms of the acids are alsowithin the purview of the invention.

One or more differently structured monomers may be used as the Econstituent provided that they fall within the definition of E abovegiven. One such preferred mixture of E monomers would be acrylicacid/2-hydroxypropyl acrylate.

R₁ in the above formula (Formula I) is a hydroxy substituted loweralkylene group having from about 1 to 6 carbon atoms or anon-substituted lower alkylene group having from 1 to 6 carbon atoms. Min Formula I is hydrogen, a water soluble cation (e.g., NH₄₊, alkalimetal) or a non-substituted lower alkyl group having from 1 to 3 carbonatoms.

Polymer structure of the present invention is disclosed in U.S.application Ser. No. 545,563.

PRIOR ART

The nomenclature of phosphorous compounds is sometimes ambiguous. Toclarify the notations, we are following the teachings by G. M.Kosolapoff in Organophosphorous Compounds (Wiley, 1950, pages 3 and 4)and by Emsley and Hall in The Chemistry of Phosphorus (Harper and Row,1976, pages 512-515): "the acids in which phosphorous has the oxidationstate (III) have the `-ous` ending and their salts and esters have the`-ite` ending. Those with oxidation state (V) have corresponding `-ic`and `-ate` endings. P(OH)₃ is called phosphorous acid although it existsin the rearranged form HP(O)(OH)₂ which is phosphonic acid. MeP(O)(OEt)₂with a C-P linkage is referred as diethyl methane phosphonate and (MeO)₂P(O)OH with two C-O-P linkages is dimethyl phosphate and (EtO)₂ POHwhich can have a P-H bond is diethyl phosphite".

U.S. Pat. No. 4,500,693 (Takehara, et. al.) discloses sundry copolymerscomposed of a (meth) acrylic acid monomer and an allylic ether monomer.Such polymers are disclosed as being useful dispersants and scalepreventing agents that may be used in cooling water or water collectionsystems, etc. In accordance with the '693 disclosure, the allylic ethermonomer may include, inter alia, the reaction product of allyloxydihydroxypropane with various reagents, such as, ethylene oxide,phosphorus pentoxide, propylene oxide, monoaryl sorbitan, etc. Whenphosphorus pentoxide is reacted with allyloxydihydroxypropane, theresulting product is reported to contain phosphate functionality, i.e.,with a C-O-P linkage.

U.S. Pat. Nos 4,659,480 and 4,708,815 (Chen et. al., continuation ofSer. No. 545,563) disclose the reaction of allyl glycidyl ether withphosphorus acid (H₃ PO₃) which results to allyloxy hydroxypropylphosphite with a distinct C-O-P-H structure. Water soluble copolymer andterpolymer are then prepared using the phosphite containing monomer.These disclosures are in contrast to the phosphonate functionalitybonded to the polymer matrix in accordance with the present invention,where the linkage is C-PO₃ H₂.

U.S. Pat. No. 4,046,707 (Smith et al.) describes polyacrylic acidcontaining one terminal phosphonate group or one internal phosphonategroup. The precise structure of their disclosed compounds are difficultto identify due to the vague ³¹ P NMR information given in thereference. The polymerization procedure in the present invention ismarkedly different from Smith or Takehara. The phosphonate monomer isisolated first, then copolymerized it with acrylic acid to form apolymer containing multiple phosphonate groups.

Of further interest to the present invention is U.S. Pat. No. 4,207,405(Masler, et al.) wherein water treatment usage of certain phosphorousacid/carboxylic polymer reaction products is taught. Specific teachingsof this reference include reaction of poly (meth) acrylic acid withphosphorous acid or precursor thereof to yield a hydroxydiphosphonicacid adduct with the polymer. The disclosed reaction must be carried outunder anhydrous conditions, with the product then being hydrolyzed in anaqueous medium. The precise structure of the reaction product isdifficult to identify and contains only low levels of phosphorussubstitution.

Of lesser interest are U.S. Pat. Nos. 3,262,903 (Robertson) and2,723,971 (Cupery) which teach reaction of a polyepoxide withorthophosphoric acid to provide a polymer having a phosphoric acid estersubstituent. The resulting polymeric phosphate is soluble in organicsolvents and is useful as a film forming ingredient in coatingcompositions. It cannot be used in the water treatment field whereinwater solubility is an essential criterion.

Other prior art patents and publications which may be of interestinclude: Japanese Pat. No. 56-155692, U.S. Pat. No. 4,678,840 (Fong, etal.) and U.S. Pat. No. 4,650,591 (Boothe, et al.). In the '840 and '591patents, phosphonate group bonded to a vinyl amide moiety is disclosed.They are different structures than the present invention where ahydroxylated alkylene allyl ether is connected to the phosphonate group.The allyl ether linkage is also more hydrolytically and thermally stablethan the amide linkage.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, new water soluble copolymers andterpolymers, as shown in Formula I hereinafter, are synthesized. Thewater soluble copolymers and terpolymers of the invention compriserepeat units having the structures: ##STR2## wherein E in the aboveformula is the repeat unit after polymerization of and α, βethylenicallyunsaturated compound, preferably carboxylic acid, amide form thereof, orlower alkyl (C₁ -C₆) ester or hydroxylated lower alkyl (C₁ -C₆) ester ofsuch carboxylic acid. Compounds encompassed by E include the repeat unitafter polymerization of acrylic acid, methacrylic acid, acrylamide,maleic acid or anhydride, styrene, styrene sulfonic acid and itaconicacid, and the like. Water soluble salt forms of the acids are alsowithin the purview of the invention.

One or more differently structured monomers may be used as the Econstituent provided that they fall within the definition of E abovegiven. One such preferred mixture of E monomers would be acrylicacid/2-hydroxypropyl acrylate.

R₁ in the above formula (Formula I) is a hydroxy substituted loweralkylene group having from about 1 to 6 carbon atoms or anon-substituted lower alkylene group having from 1 to 6 carbon atoms. Min Formula I is hydrogen, a water soluble cation (e.g., NH₄ +, alkalimetal), or a non-substituted lower alkyl group having from 1 to 3 carbonatoms.

The molar ratio of the monomers (g:h) of Formula I may fall within therange of 30:1 to 1:20, with a molar ratio (g:h) of about 10:1 to 1:5being preferred.

The number average molecular weight of the water soluble copolymers ofFormula I may fall within the range of 1,000 to 1,000,000. Preferably,the number average molecular weight will be within the range of about1,500 to about 500,000. The key criterion is that the polymer be watersoluble.

As to preparation of the monomer designated as g hereinabove, these maybe in accordance with well known techniques. For instance, one suchpossible monomer, acrylic acid, may be prepared by hydrolysis ofacrylonitrile or by oxidation of acrolein.

As to the allyl monomer (monomer h), this may be prepared in accordancewith the disclosure of U.S. Pat. No. 4,659,481 (sections 3 and 4) usingallyl glycidyl ether (AGE) as a reactant, or it may more preferably beprepared by a ring opening reaction using diethyl oxiranylmethylphosphonate precursor to prepare the diethyl 1-allyloxy hydroxypropylphosphonate monomer. This is then followed by dealkylation of thephosphonate ester to prepare the preferred allyloxy hydroxy phosphonicacid. To prepare the other acceptable 1-allyloxy hydroxyl (C₁ -C₆)phosphonate monomers, the skilled artisan will simply utilize thecorresponding epoxide.

Diethyl oxiranylmethyl phosphonate is reacted with allyl alcohol to forma mixed monomer solution in accordance with the equation: ##STR3##

The reaction may be carried out in anhydrous conditions with a reactiontemperature ranging from 25° to 98° C. For each mole of epoxide used,1.0 to about 20.0 moles of allyl alcohol may be used. Allyl phosphonicacid may be present in the mixed monomer solution which is from thepresence of residual diethyl allyl phosphonate (associated with diethyloxiranylmethyl phosphonate).

The IUPAC nomenclature for diethyl epoxymethyl phosphonate is phosphonicacid, (oxiranylmethyl)-diethyl ester [CAS registry number: 7316-37-2],which can be prepared from the epoxidation of diethyl allyl phosphonatein accordance to the equation: ##STR4##

A small amount of unreacted diethyl allyl phosphonate may be presentafter the reaction. Without further purification, this diester willhydrolyze to allyl phosphonic acid and be copolymerized with monomers Eand h in Formula 1.

The structures of the preferred allyloxy hydroxypropyl phosphonates(AHPPO) were substantiated by 31P and 13C NMR spectroscopy and IRspectra. The 31P NMR spectra showed a major resonance at 28.65 and aminor resonance at 29.00 ppm downfield from the external phosphoric acidstandard. These were assigned to the primary and secondary isomers ofallyloxy hydroxypropyl phosphonates (AHPPO), respectively. A resonanceat 28.13 ppm was assigned as allyl phosphonic acid (APA). A trace amountof phosphate and phosphonate compounds were noted at 1.32, 30.50 and35.58 ppm. The ¹³ C NMR showed the primary AOHPP at 31.00 (J =137 Hz),65.58, 71.87, 73.71 (J =14 Hz), 118.29, and 133.90 ppm downfield fromexternal dioxane. Allyl phosphonic acid was detected at 32.0 (J =133Hz), 120.0 and 128.0 ppm. The IR spectra showed a weak C-P stretch at770 cm-1.

It is noted that the Na ion present in the AHPPO monomer above may bereplaced with hydrogen, K, NH₄ +, or any water soluble cation. The Naion may also be replaced by an organic amine group or lower alkyl groupof from about 1-3 carbon atoms. The molar ratio of the AGE:AHPPOcomponents in the mixed monomer solution may be varied to result indifferent ratios of these two components in the resulting polymer.

If desired, allyl phosphonic acid may be removed from the mixed monomersolution (i.e., leaving an aqueous solution of the two AHPP monomers)via distillation, solvent extraction, etc. At present, it is preferredto utilize the mixed monomer solution as it is produced (which thereforeincludes allyl phosphonic acid (APA)). In such cases, afterpolymerization, the resulting polymer comprises allyl phosphonic acid(APA) which incorporates into the polymeric matrix along with the AHPPOisomers. When the APA component of the mixed monomer solution is notremoved, the resulting polymer may comprise:

    ______________________________________                                                             mole %                                                   ______________________________________                                        α, βethylenically unsaturated monomer                                                     40-90                                                  APA                    0-25                                                   AHPPO                  2-50                                                   ______________________________________                                    

with the foregoing adding up to 100 mole %.

When allyl glycidyl ether (AGE) is used as a reagent to prepare theAHPPO monomer in accordance with the disclosure of U.S. Pat. No.4,659,481, glyceryl allyl ether (hydrolysis product of AGE) may beformed. Similarly, glyceryl allyl ether may be separated from thepreferred monomer h or be copolymerized with monomers g and h ofFormula 1. Therefore, they are also within the scope of this invention.

After the desired monomers are produced and isolated, radicalpolymerization may proceed in solution, suspension, bulk, emulsion orthermal polymerization form. For instance, in suspension polymerization,the reaction may be initiated by an azo compound or an organic peroxide,with the monomers suspended in hexane or other organic reagents. On theother hand, in solution polymerization, the reaction may be initiatedvia conventional persulfate or peroxide initiators. Commonly used chaintransfer agents such as lower alkyl alcohols, amines or mercaptocompounds may be used to regulate the molecular weight. An acceleratorsuch as sodium bisulfite or ascorbic acid may also be used.

The fact that polymers were formed by the above method was substantiatedby viscosity increase, gel permeation chromatography, ¹³ C and ³¹ P NMRspectroscopy. The ¹³ C NMR spectra showed a broad, polymer type backbonewith complex C-O region (62-74 ppm) and no evidence of unreactedmonomers. The ³¹ P NMR spectra were similar to that of allyloxyhydroxypropyl phosphonate but with broader absorption, an indication ofpolymer formation.

Since, in accordance with the preferred method for obtaining thephosphonate monomer, minor amounts of allyl phosphonic acid mayincorporate into the polymeric matrix when the preferred syntheticroute, including use of the mixed monomer solution is used, theresulting polymer comprises repeat units having the structures: ##STR5##wherein g, h an M are the same as in Formula I. R₂ is a lower alkylenegroup having from about 1-4 carbon atoms. Monomer i may be present in amolar amount of between about 0-25%, with monomer g being present in amolar amount of between about 40-90%. Monomer h is present in an amountof about 2-50%. All foregoing molar percentages should add up to 100%.

It should be mentioned that other water soluble terpolymers comprisingmonomers E and h of Formula II may also be prepared. For instance,1-allyloxy-2-hydroxypropyl sulfonate may be incorporated into a watersoluble terpolymer backbone having repeat units from E and h. Therefore,it is also within the scope of the invention.

The specific preferred polymer is a terpolymer of acrylic acid/allyloxyhydroxypropyl phosphonic acid/allyl phosphonic acid (present in only aminor amount) comprising repeat units having the structures: ##STR6##

The polymers should be added to the aqueous system, for which depositcontrol activity or inhibiting the corrosion of metal parts in contactwith an aqueous medium, is desired, in an amount effective for thepurpose. This amount will vary depending upon the particular system forwhich treatment is desired and will be influenced by factors such as,the area subject to deposition, pH, temperature, water quantity and therespective concentrations in the water of the potential scale anddeposit forming species. For the most part, the polymers will beeffective when used at levels of about 0.1-500 parts per million partsof water, and preferably from about 1.0 to 100 parts per million ofwater contained in the aqueous system to be treated. The polymers may beadded directly into the desired water system in a fixed quantity and inthe state of an aqueous solution, continuously or intermittently.

The polymers of the present invention are not limited to use in anyspecific category of water system. For instance, in addition to boilerand cooling water systems, the polymers may also be effectively utilizedin scrubber systems and the like wherein the formation and deposition ofscale forming salts is a problem. Other possible environments in whichthe inventive polymers may be used include heat distribution type seawater desalting apparatus and dust collection systems in iron and steelmanufacturing industries and as a dispersant in the pulp and paperprocessing industries. Also the polymers could be used as mineralbeneficiation aids such as in iron ore, phosphate, and potash recovery.

EXAMPLES

The invention will be further described with reference to a number ofspecific examples which are to be regarded solely as illustrative, andnot as restricting the scope of the invention.

EXAMPLE 1 Preparation of Diethyl Oxiranylmethyl Phosphonate (OMPDE)

A suitable reaction flask was equipped with a reflux condenser, magneticstirrer, thermometer, nitrogen inlet and addition port. 52 g of 90%diethyl allyl phosphonate (0.26 mole) and 865 g of chloroform werecharged to the flask. 64 g of 85% m-chloroperbenzoic acid (0.32 mole)was then added to the flask over a 20 minute period at 3°-5° C. under anitrogen blanket. After addition, the batch was stirred at roomtemperature for 88 hours and then cooled to 3° C. The resulting mixturewas filtered, and then the filtrate was washed with aqueous sodiumbisulfite, aqueous sodium bicarbonate, brine and dried (MgSO₄). Theorganic layer was then concentrated under reduced pressure and distilledthrough a Vigreux column at 1 mm Hg and 100°-103° C. The resultingproduct was identified by ¹³ C and ³¹ P NMR as mainly diethyloxiranylmethyl phosphonate (OMPDE, 92%).

The 31P NMR showed a major resonance at 27.9 ppm downfield from theexternal phosphoric acid standard which was assigned to the OMPDE.Residual diethyl allyl phosphonate was observed at 28.1 ppm. A traceamount of phosphate and phosphonate species were also noted at 0.9 and34.4 ppm. The ¹³ C NMR showed the OMPDE at 15.9, 29.2 (J =137 Hz), 46.1,46.2 and 61.0 ppm downfield from external dioxane standard. Diethylallyl phosphonate was detected at 31.5 (J=139 Hz), 118.9, and 128.7 ppm.

EXAMPLE 2 Preparation of Diethyl Allyloxy Hydroxypropyl Phosphonate(AHPPODE) and Diethyl Allyl Phosphonate Mixed Monomer Solution

Utilizing the apparatus described in Example 1, 39 g of product fromExample 1 (92% OMPDE, 0.19 mole) and 200 g of allyl alcohol (3.41 mole)were charged to the flask and heated at reflux for about 60 hours. Afterreaction, residual allyl alcohol was removed via distillation to yield acolorless liquid (48 g). The product contained mainly diethyl allyloxyhydroxypropyl phosphonate (AHPPODE, 90%) and some diethyl allylphosphonate as verified by NMR.

The ³¹ P NMR spectrum showed a major resonance at 31.9 ppm which wasassigned to AHPPODE. Diethyl allyl phosphonate (28.9 ppm) and either thesecondary isomer of AHPPODE, or diethyl 2,3-dihydroxypropyl phosphonate(from hydrolysis of the OMPDE) (32.5 ppm) was also detected. A smallamount of phosphate and phosphonate compounds were noted at 0.9 and 35.3ppm. The ¹³ C NMR showed the AHPPODE at 16.1, 30.5 (J =139 Hz), 61.2,65.3, 71.7, 74.4 (J=13 Hz), 115.6 and 135.3 ppm. Diethyl allylphosphonate was detected at 119 and 129 ppm. A trace of residual allylalcohol (62.4, 112.9 and 140 ppm) was also observed.

EXAMPLE 3 Preparation of Allyloxy Hydroxypropyl Phosphonic Acid (AHPPO)and Allyl Phosphonic Acid (APA) Mixed Monomer Solution

Utilizing the apparatus described in Example 1, 48 g of solution ofExample 2 (90% AOHPPA, 0.17 mole) and 270 g of dried carbontetrachloride were charged to the reaction flask. 95 g ofbromotrimethylsilane (0.61 mole) was then added over one hour whilemaintaining a temperature of 16°C. After the addition, the batch washeated at 40° C. for 90 minutes and then concentrated in vacuo. Methanoland deionized water were then added and the solution was againconcentrated in vacuo to yield a clear liquid (53 g). The weight of theproduct was then adjusted to 100 g with deionized water. The product wasidentified by ¹³ C and ³¹ P NMR as containing mainly allyloxyhydroxypropyl phosphonate (AHPPO, 88%). The concentration of thesolution was analyzed to be 34.4% solids.

The ³¹ P NMR spectrum showed a major resonance at 28.65 ppm which wasassigned to the primary AHPPO. Two minor resonances at 29.00 ppm and28.13 ppm were assigned the secondary AHPPO isomer and allyl phosphonicacid (APA), respectively. A trace amount of other phosphate andphosphonate compounds were also noted at 1.32, 30.50 and 35.58 ppm. The¹³ C NMR showed the primary AHPPO at 31.00 (J=137 Hz), 65.58, 71.87,73.71 (J =14 Hz), 118.29, and 133.90 ppm. Allyl phosphonic acid wasdetected at 32.0 (J =133 Hz), 120.0 and 128.0 ppm. The IR spectrumshowed a weak C-P stretch at 770 cm-1.

EXAMPLE 4 Preparation of Acrylic Acid/Allyloxy Hydroxypropyl PhosphonicAcid/Allyl Phosphonic Acid Terpolymer Molar Ratio 6.42/1.00/0.11

Utilizing the apparatus described in Example 1, but with an overheadstirrer, 24.26 g of the mixed monomer solution from Example 3 (0.0374mole of AHPPO, and 0.0041 mole of APA), 36.96 g of deionized water and1.28 g of isopropanol were charged to the flask. The resulting solutionwas then heated to a slight reflux (95° C.) under a nitrogen blanket.17.65 g of acrylic acid (0.24 mole) and 12.05 g of sodium persulfatesolution (17%) were then charged to the flask over a period of 3.5hours. After the addition, the reaction mixture was held at a slightreflux for 1.5 hours, followed by the removal of 7.71 g of anisopropanol/water azeotrope. The reaction mixture was then cooled toroom temperature.

The terpolymer solution, after being diluted with water to 25% solids,had a Brookfield viscosity of 26 cps at 25 C. The resulting product wasslightly hazy with a light yellow color. The structure of the terpolymerwas verified by 13C NMR. The spectrum was characterized by a broad,polyacrylic acid type backbone, complex C-O region (62-74 ppm), broadcarbonyl region (178 ppm) and a resonance at 30.8 ppm (J =136 Hz). The31P NMR spectrum was similar to that described in Example 3 except therewas a broadening in the width of the peaks which indicates that theAHPPO incorporated into the polymer.

Passivation

Although the polymers of the invention, when used singly, may notadequately inhibit corrosion, the demonstrated efficacy of polymers ofsimilar structure (see U.S. Pat. No.4,659,481) in inhibiting calciumphosphate precipitation is very important. For instance, onesuccessfully established cooling water treatment method provides apassivated film on metal surfaces in contact with the aqueous medium viaaddition of orthophosphate, organo-phosphonate and an acrylicacid/hydroxylated alkyl acrylate copolymer. Details of such method aredisclosed in U.S. Pat. No. 4,303,568 (May et. al.). The entire contentof this patent is hereby incorporated by reference. Based upon thedeposit control efficacy shown by the instant copolymers, as well as theminimum corrosion rates displayed herein in the recirculator studies, itis thought that the subject copolymers can be substituted for thepolymers disclosed in the aforementioned May et al. patent so as toprovide the important passivated film on the desired metal surfaces.

As is stated in the May et al. patent, the passive film is provided onmetal surfaces in contact with the aqueous medium without substantialattendant deposition formed thereon. A composition containing polymerand orthophosphate and optionally but preferably a phosphonate,polyphosphate and copper corrosion inhibitors is used in order toachieve such passivation. A typical composition contains on a weightratio basis of polymer to orthophosphate expressed as PO₄ -- of about1:8 to 4:1 and preferably about 1:6 to 2:1. When a polyphosphate* isincluded, the weight ratio of orthophosphate phosphate to polyphosphateon a PO₄ --basis is 15:1 to 1:3, and preferably 2.3:1 to 1:1. Similarly,if the organo-phosphonate is included, the ratio of the orthophosphateto the phosphonate expressed as PO₄ -- to PO₄ -- is 1:2 to 13:1, andpreferably 2:1 to 8:1. Any copper corrosion inhibitor may be included inthe composition (0.01 to 5% by weight) in an amount which will beeffective for controlling the copper corrosion in a given system: 0.05to 10 parts per million and preferably 0.5 to 5 parts per million.Similarly, zinc salts may be included if additional protection isneeded.

In treating the aqueous systems to provide such passivation, thefollowing dosages in parts per million parts of water in said aqueoussystems of the respective ingredients are desirable, with the dosages,of course, being based upon the severity of the corrosion problemforeseen or experienced:

orthophosphate (expressed as PO₄ --): 2 to 50 parts per million parts ofwater (ppm) and preferably 6 to 30 ppm;

polymer: 0.3 to 120 ppm and preferably 3 to 25 ppm;

polyphosphate (expressed as PO₄ --): 0.1 to 30, and preferably 3 to 10,parts per million parts of water;

phosphonate (expressed as PO₄ --): 0.04 to 20, and preferably 1 to 6,parts per million parts of water.

The preferred rate of application of this treatment to cooling watersystems and the ratios of various components depends on the calciumconcentration of the cooling water. The treatment is preferably appliedin waters having between 15 ppm and 1,000 ppm calcium. Within this rangethe weight ratio of calcium to orthophosphate is varied from 1:1 to83.3:1, the weight ratio of polymer to orthophosphate is varied from 1:3to 1.5:1.

The orthophosphate which is critical to passivation aspect of thepresent invention is generally obtained by direct addition. However, itis understood that the orthophosphate can also arise due to reversion ofeither inorganic polyphosphates or the organo-phosphonates, or any otherappropriate source or precursor thereof.

The above dosages represent the most desirable ranges since most systemswill be treatable therewith. Higher dosages are permissible when thesituation demands, but of course are most costly. The effectiveness ofthe inventive treatments are dependent upon the aqueous medium having apH of 5.5 and above, and preferably 6.5 to 9.5, and containing calciumion concentrations, preferably about 15 parts per million parts ofwater. Below this range, it may be necessary for overall effectivenessto add metallic ions such as zinc, nickel, chromium, etc. as describedin column 3, lines 4 to 24 of U.S. Pat. No. 3,837,803.

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

We claim:
 1. Composition comprising a water soluble polymer, saidpolymer comprising substantially repeat units having the structure##STR7## wherein E in the above formula is the repeat unit obtainedafter polymerization of an α, βethylenically unsaturated compound. R₁ isa hydroxy substituted lower alkylene group having from about 1-6 carbonatoms or a non-substituted lower alkylene group having from about 1-6carbon atoms; M is a water soluble cation, hydrogen or an alkyl grouphaving from 1 to 3 carbon atoms wherein R₂ comprises a lower alkylene(C₁ -C₄) group and the molar percentage of g in said polymer beingbetween about 40-90 molar %, the molar percentage of h being between2-50 molar percentage and the molar percentage of i in said polymerbeing between about 0-25 molar %, the total of g, h and i equalling 100molar %.
 2. Composition as recited in claim 1 wherein E comprises therepeat unit remaining after polymerization of a compound or compoundsselected from the group consisting of acrylic acid, acrylamide, maleicacid or anhydride, itaconic acid, methacrylic acid, lower alkyl (C₁ -C₆)ester or hydroxylated lower alkyl (C₁ -C₆) ester of said acids. 3.Composition as recited in claim 2 wherein E comprises acrylic acidrepeat unit and 2-hydroxypropylacrylate repeat unit.
 4. Composition asrecited in claim 1 wherein E comprises acrylic acid repeat unit, R₁comprises 2-hydroxypropylene and R₂ comprises methylene.
 5. Compositionas recited in claim 1 further comprising a water soluble orthophosphatecompound said composition comprising, on a weight ratio basis from about1:8 to about 4:1 polymer:orthophosphate.
 6. Composition as recited inclaim 5 further comprising a water soluble polyphosphate compound, theweight ratio of orthophosphate:polyphosphate being in the range of about15:1 to 1:3.
 7. Composition as recited in claim 1 wherein M comprises amember selected from the group consisting of H, Na, K, NH₄ ⁺, an organicamine group, or an alkyl group having from 1 to 3 carbon atoms.